Family I34
Summary for family I34
| Name | Inhibitor family I34 (IA3 family) |
|---|
| Family type peptidase | I34.001 - saccharopepsin inhibitor (Saccharomyces cerevisiae), MEROPS Accession MER0018444 (inhibitor unit: 1-68) |
| Content of family | Inhibitor family I34 contains only saccharopepsin inhibitor (I34.001) from Saccharomyces cerevisiae. |
| History |
Identifier created: MEROPS 6.1 (10 January 2003)
Inhibition of saccharopepsin (A01.018) was first described by Saheki et al. (1974) |
| Peptidases inhibited | Saccharopepsin inhibitor is highly specific for the aspartic peptidase saccharopepsin. Other family A1 members such as human pepsin, human cathepsins D and E, and yeast yapsin are not inhibited by saccharopepsin inhibitor, but cleave it (Phylip et al., 2001). |
| Mechanism of inhibition | When saccharopepsin inhibitor undergoes conformational change and occupies the active site cleft of saccharopepsin, the epsilon-NH2 group of Lys18 forms a hydrogen bond with the carbonyl oxygen of Asp32 in the peptidase and also with one of the side chain carbonyl oxygen atoms of Asp22 in the inhibitor (Phylip et al., 2001). In addition, the second side chain carbonyl oxygen of Asp22 hydrogen bonds to the phenolic OH group of Tyr75 on the saccharopepsin flap - a residue conserved in nearly all eukaryotic aspartic peptidases. No inhibitory activity is found within the C-terminal section of the inhibitor (Li et al., 2000). |
| Molecular structure | Saccharopepsin inhibitor is 68 amino acid in length and is largely unstructured in the absence of saccharopepsin (Green et al., 2004). However, in its presence the inhibitor undergoes a conformation change, forming an almost perfect alpha-helix from Asn2 to Met32 in the active site cleft of the peptidase. |
| Clan | JA |
|
Distribution of family
|
Bacteria |
- |
|
|
|
Archaea |
- |
|
|
|
Protozoa |
- |
|
|
|
Fungi |
- |
|
|
|
Plants |
details |
|
|
|
Animals |
- |
|
|
|
Viruses |
- |
|
